1. Field of the Invention
This invention relates to fluid flow valves, and more particularly, to a fluid flow control valve having redundant valve members and regulating apparatus which provides slow opening for the valve.
2. Description of the Prior Art
In heating systems of the pilot ignition type, a pilot valve is energized in response to a request for heat, supplying pilot gas to a pilot outlet for ignition to establish a pilot flame. Once the pilot flame is proven, a main gas valve is operated to supply gas to a main burner apparatus located within a combustion box of a furnace, for ignition by the pilot flame.
There is a trend in the heating industry to provide furnaces which have small combustion boxes. In such furnaces, when the pilot is proven and the main gas valve is energized to supply gas to the main burner apparatus, the main gas valve opens rapidly, supplying gas at maximum pressure to the main gas burner apparatus. In furnaces having small combustion boxes, there may be a small explosion or rollout of gas flames from the chamber accompanied by a loud noise. Such condition is undesirable from a customer's standpoint. Accordingly, it would be desirable to have a gas valve which regulates the flow of gas supplied to a main gas burner apparatus prior to ignition, such that upon operation of the main gas valve, gas is supplied to the main gas burner apparatus at low pressure for ignition, and the pressure of the gas supplied to the burner apparatus is thereafter gradually increased to the system pressure.